/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package java.nio;

import java.io.IOException;

/**
 * A buffer of chars.
 *
 * <p>A char buffer can be created in either one of the following ways:
 *
 * <ul>
 *   <li>{@link #allocate(int) Allocate} a new char array and create a buffer based on it;
 *   <li>{@link #wrap(char[]) Wrap} an existing char array to create a new buffer;
 *   <li>{@link #wrap(CharSequence) Wrap} an existing char sequence to create a new buffer;
 *   <li>Use {@link java.nio.ByteBuffer#asCharBuffer() ByteBuffer.asCharBuffer} to create a char
 *       buffer based on a byte buffer.
 * </ul>
 *
 * @since Android 1.0
 */
public abstract class CharBuffer extends Buffer
    implements Comparable<CharBuffer>, CharSequence, Appendable { // , Readable {

  /**
   * Creates a char buffer based on a newly allocated char array.
   *
   * @param capacity the capacity of the new buffer.
   * @return the created char buffer.
   * @throws IllegalArgumentException if {@code capacity} is less than zero.
   * @since Android 1.0
   */
  public static CharBuffer allocate(int capacity) {
    if (capacity < 0) {
      throw new IllegalArgumentException();
    }
    return BufferFactory.newCharBuffer(capacity);
  }

  /**
   * Creates a new char buffer by wrapping the given char array.
   *
   * <p>Calling this method has the same effect as {@code wrap(array, 0, array.length)}.
   *
   * @param array the char array which the new buffer will be based on.
   * @return the created char buffer.
   * @since Android 1.0
   */
  public static CharBuffer wrap(char[] array) {
    return wrap(array, 0, array.length);
  }

  /**
   * Creates a new char buffer by wrapping the given char array.
   *
   * <p>The new buffer's position will be {@code start}, limit will be {@code start + len}, capacity
   * will be the length of the array.
   *
   * @param array the char array which the new buffer will be based on.
   * @param start the start index, must not be negative and not greater than {@code array.length}.
   * @param len the length, must not be negative and not greater than {@code array.length - start}.
   * @return the created char buffer.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code len} is invalid.
   * @since Android 1.0
   */
  public static CharBuffer wrap(char[] array, int start, int len) {
    int length = array.length;
    if ((start < 0) || (len < 0) || start + len > length) {
      throw new IndexOutOfBoundsException();
    }

    CharBuffer buf = BufferFactory.newCharBuffer(array);
    buf.position = start;
    buf.limit = start + len;

    return buf;
  }

  /**
   * Creates a new char buffer by wrapping the given char sequence.
   *
   * <p>Calling this method has the same effect as {@code wrap(chseq, 0, chseq.length())}.
   *
   * @param chseq the char sequence which the new buffer will be based on.
   * @return the created char buffer.
   * @since Android 1.0
   */
  public static CharBuffer wrap(CharSequence chseq) {
    return BufferFactory.newCharBuffer(chseq);
  }

  /**
   * Creates a new char buffer by wrapping the given char sequence.
   *
   * <p>The new buffer's position will be {@code start}, limit will be {@code end}, capacity will be
   * the length of the char sequence. The new buffer is read-only.
   *
   * @param chseq the char sequence which the new buffer will be based on.
   * @param start the start index, must not be negative and not greater than {@code chseq.length()}.
   * @param end the end index, must be no less than {@code start} and no greater than {@code
   *     chseq.length()}.
   * @return the created char buffer.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid.
   * @since Android 1.0
   */
  public static CharBuffer wrap(CharSequence chseq, int start, int end) {
    if (chseq == null) {
      throw new NullPointerException();
    }
    if (start < 0 || end < start || end > chseq.length()) {
      throw new IndexOutOfBoundsException();
    }

    CharBuffer result = BufferFactory.newCharBuffer(chseq);
    result.position = start;
    result.limit = end;
    return result;
  }

  /**
   * Constructs a {@code CharBuffer} with given capacity.
   *
   * @param capacity the capacity of the buffer.
   * @since Android 1.0
   */
  CharBuffer(int capacity) {
    super(capacity);
  }

  /**
   * Returns the char array which this buffer is based on, if there is one.
   *
   * @return the char array which this buffer is based on.
   * @exception ReadOnlyBufferException if this buffer is based on an array, but it is read-only.
   * @exception UnsupportedOperationException if this buffer is not based on an array.
   * @since Android 1.0
   */
  public final char[] array() {
    return protectedArray();
  }

  /**
   * Returns the offset of the char array which this buffer is based on, if there is one.
   *
   * <p>The offset is the index of the array corresponds to the zero position of the buffer.
   *
   * @return the offset of the char array which this buffer is based on.
   * @exception ReadOnlyBufferException if this buffer is based on an array but it is read-only.
   * @exception UnsupportedOperationException if this buffer is not based on an array.
   * @since Android 1.0
   */
  public final int arrayOffset() {
    return protectedArrayOffset();
  }

  /**
   * Returns a read-only buffer that shares its content with this buffer.
   *
   * <p>The returned buffer is guaranteed to be a new instance, even if this buffer is read-only
   * itself. The new buffer's position, limit, capacity and mark are the same as this buffer's.
   *
   * <p>The new buffer shares its content with this buffer, which means this buffer's change of
   * content will be visible to the new buffer. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a read-only version of this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer asReadOnlyBuffer();

  /**
   * Returns the character located at the specified index in the buffer. The index value is
   * referenced from the current buffer position.
   *
   * @param index the index referenced from the current buffer position. It must not be less than
   *     zero but less than the value obtained from a call to {@code remaining()}.
   * @return the character located at the specified index (referenced from the current position) in
   *     the buffer.
   * @exception IndexOutOfBoundsException if the index is invalid.
   * @since Android 1.0
   */
  public final char charAt(int index) {
    if (index < 0 || index >= remaining()) {
      throw new IndexOutOfBoundsException();
    }
    return get(position + index);
  }

  /**
   * Compacts this char buffer.
   *
   * <p>The remaining chars will be moved to the head of the buffer, starting from position zero.
   * Then the position is set to {@code remaining()}; the limit is set to capacity; the mark is
   * cleared.
   *
   * @return this buffer.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer compact();

  /**
   * Compare the remaining chars of this buffer to another char buffer's remaining chars.
   *
   * @param otherBuffer another char buffer.
   * @return a negative value if this is less than {@code otherBuffer}; 0 if this equals to {@code
   *     otherBuffer}; a positive value if this is greater than {@code otherBuffer}.
   * @exception ClassCastException if {@code otherBuffer} is not a char buffer.
   * @since Android 1.0
   */
  public int compareTo(CharBuffer otherBuffer) {
    int compareRemaining =
        (remaining() < otherBuffer.remaining()) ? remaining() : otherBuffer.remaining();
    int thisPos = position;
    int otherPos = otherBuffer.position;
    char thisByte, otherByte;
    while (compareRemaining > 0) {
      thisByte = get(thisPos);
      otherByte = otherBuffer.get(otherPos);
      if (thisByte != otherByte) {
        return thisByte < otherByte ? -1 : 1;
      }
      thisPos++;
      otherPos++;
      compareRemaining--;
    }
    return remaining() - otherBuffer.remaining();
  }

  /**
   * Returns a duplicated buffer that shares its content with this buffer.
   *
   * <p>The duplicated buffer's initial position, limit, capacity and mark are the same as this
   * buffer's. The duplicated buffer's read-only property and byte order are the same as this
   * buffer's, too.
   *
   * <p>The new buffer shares its content with this buffer, which means either buffer's change of
   * content will be visible to the other. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a duplicated buffer that shares its content with this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer duplicate();

  /**
   * Checks whether this char buffer is equal to another object.
   *
   * <p>If {@code other} is not a char buffer then {@code false} is returned. Two char buffers are
   * equal if and only if their remaining chars are exactly the same. Position, limit, capacity and
   * mark are not considered.
   *
   * @param other the object to compare with this char buffer.
   * @return {@code true} if this char buffer is equal to {@code other}, {@code false} otherwise.
   * @since Android 1.0
   */
  public boolean equals(Object other) {
    if (!(other instanceof CharBuffer)) {
      return false;
    }
    CharBuffer otherBuffer = (CharBuffer) other;

    if (remaining() != otherBuffer.remaining()) {
      return false;
    }

    int myPosition = position;
    int otherPosition = otherBuffer.position;
    boolean equalSoFar = true;
    while (equalSoFar && (myPosition < limit)) {
      equalSoFar = get(myPosition++) == otherBuffer.get(otherPosition++);
    }

    return equalSoFar;
  }

  /**
   * Returns the char at the current position and increases the position by 1.
   *
   * @return the char at the current position.
   * @exception BufferUnderflowException if the position is equal or greater than limit.
   * @since Android 1.0
   */
  public abstract char get();

  /**
   * Reads chars from the current position into the specified char array and increases the position
   * by the number of chars read.
   *
   * <p>Calling this method has the same effect as {@code get(dest, 0, dest.length)}.
   *
   * @param dest the destination char array.
   * @return this buffer.
   * @exception BufferUnderflowException if {@code dest.length} is greater than {@code remaining()}.
   * @since Android 1.0
   */
  public CharBuffer get(char[] dest) {
    return get(dest, 0, dest.length);
  }

  /**
   * Reads chars from the current position into the specified char array, starting from the
   * specified offset, and increases the position by the number of chars read.
   *
   * @param dest the target char array.
   * @param off the offset of the char array, must not be negative and not greater than {@code
   *     dest.length}.
   * @param len The number of chars to read, must be no less than zero and no greater than {@code
   *     dest.length - off}.
   * @return this buffer.
   * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid.
   * @exception BufferUnderflowException if {@code len} is greater than {@code remaining()}.
   * @since Android 1.0
   */
  public CharBuffer get(char[] dest, int off, int len) {
    int length = dest.length;
    if ((off < 0) || (len < 0) || len > length - off) {
      throw new IndexOutOfBoundsException();
    }

    if (len > remaining()) {
      throw new BufferUnderflowException();
    }
    for (int i = off; i < off + len; i++) {
      dest[i] = get();
    }
    return this;
  }

  /**
   * Returns a char at the specified index; the position is not changed.
   *
   * @param index the index, must not be negative and less than limit.
   * @return a char at the specified index.
   * @exception IndexOutOfBoundsException if index is invalid.
   * @since Android 1.0
   */
  public abstract char get(int index);

  /**
   * Indicates whether this buffer is based on a char array and is read/write.
   *
   * @return {@code true} if this buffer is based on a byte array and provides read/write access,
   *     {@code false} otherwise.
   * @since Android 1.0
   */
  public final boolean hasArray() {
    return protectedHasArray();
  }

  /**
   * Calculates this buffer's hash code from the remaining chars. The position, limit, capacity and
   * mark don't affect the hash code.
   *
   * @return the hash code calculated from the remaining chars.
   * @since Android 1.0
   */
  public int hashCode() {
    int myPosition = position;
    int hash = 0;
    while (myPosition < limit) {
      hash = hash + get(myPosition++);
    }
    return hash;
  }

  /**
   * Indicates whether this buffer is direct. A direct buffer will try its best to take advantage of
   * native memory APIs and it may not stay in the Java heap, so it is not affected by garbage
   * collection.
   *
   * <p>A char buffer is direct if it is based on a byte buffer and the byte buffer is direct.
   *
   * @return {@code true} if this buffer is direct, {@code false} otherwise.
   * @since Android 1.0
   */
  public abstract boolean isDirect();

  /**
   * Returns the number of remaining chars.
   *
   * @return the number of remaining chars.
   * @since Android 1.0
   */
  public final int length() {
    return remaining();
  }

  /**
   * Returns the byte order used by this buffer when converting chars from/to bytes.
   *
   * <p>If this buffer is not based on a byte buffer, then this always returns the platform's native
   * byte order.
   *
   * @return the byte order used by this buffer when converting chars from/to bytes.
   * @since Android 1.0
   */
  public abstract ByteOrder order();

  /**
   * Child class implements this method to realize {@code array()}.
   *
   * @see #array()
   */
  abstract char[] protectedArray();

  /**
   * Child class implements this method to realize {@code arrayOffset()}.
   *
   * @see #arrayOffset()
   */
  abstract int protectedArrayOffset();

  /**
   * Child class implements this method to realize {@code hasArray()}.
   *
   * @see #hasArray()
   */
  abstract boolean protectedHasArray();

  /**
   * Writes the given char to the current position and increases the position by 1.
   *
   * @param c the char to write.
   * @return this buffer.
   * @exception BufferOverflowException if position is equal or greater than limit.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer put(char c);

  /**
   * Writes chars from the given char array to the current position and increases the position by
   * the number of chars written.
   *
   * <p>Calling this method has the same effect as {@code put(src, 0, src.length)}.
   *
   * @param src the source char array.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code src.length}.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public final CharBuffer put(char[] src) {
    return put(src, 0, src.length);
  }

  /**
   * Writes chars from the given char array, starting from the specified offset, to the current
   * position and increases the position by the number of chars written.
   *
   * @param src the source char array.
   * @param off the offset of char array, must not be negative and not greater than {@code
   *     src.length}.
   * @param len the number of chars to write, must be no less than zero and no greater than {@code
   *     src.length - off}.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code len}.
   * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer put(char[] src, int off, int len) {
    int length = src.length;
    if ((off < 0) || (len < 0) || len > length - off) {
      throw new IndexOutOfBoundsException();
    }

    if (len > remaining()) {
      throw new BufferOverflowException();
    }
    for (int i = off; i < off + len; i++) {
      put(src[i]);
    }
    return this;
  }

  /**
   * Writes all the remaining chars of the {@code src} char buffer to this buffer's current
   * position, and increases both buffers' position by the number of chars copied.
   *
   * @param src the source char buffer.
   * @return this buffer.
   * @exception BufferOverflowException if {@code src.remaining()} is greater than this buffer's
   *     {@code remaining()}.
   * @exception IllegalArgumentException if {@code src} is this buffer.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer put(CharBuffer src) {
    if (src == this) {
      throw new IllegalArgumentException();
    }
    if (src.remaining() > remaining()) {
      throw new BufferOverflowException();
    }

    char[] contents = new char[src.remaining()];
    src.get(contents);
    put(contents);
    return this;
  }

  /**
   * Writes a char to the specified index of this buffer; the position is not changed.
   *
   * @param index the index, must be no less than zero and less than the limit.
   * @param c the char to write.
   * @return this buffer.
   * @exception IndexOutOfBoundsException if index is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer put(int index, char c);

  /**
   * Writes all chars of the given string to the current position of this buffer, and increases the
   * position by the length of string.
   *
   * <p>Calling this method has the same effect as {@code put(str, 0, str.length())}.
   *
   * @param str the string to write.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than the length of string.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public final CharBuffer put(String str) {
    return put(str, 0, str.length());
  }

  /**
   * Writes chars of the given string to the current position of this buffer, and increases the
   * position by the number of chars written.
   *
   * @param str the string to write.
   * @param start the first char to write, must not be negative and not greater than {@code
   *     str.length()}.
   * @param end the last char to write (excluding), must be less than {@code start} and not greater
   *     than {@code str.length()}.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code end - start}.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer put(String str, int start, int end) {
    int length = str.length();
    if (start < 0 || end < start || end > length) {
      throw new IndexOutOfBoundsException();
    }

    if (end - start > remaining()) {
      throw new BufferOverflowException();
    }
    for (int i = start; i < end; i++) {
      put(str.charAt(i));
    }
    return this;
  }

  /**
   * Returns a sliced buffer that shares its content with this buffer.
   *
   * <p>The sliced buffer's capacity will be this buffer's {@code remaining()}, and its zero
   * position will correspond to this buffer's current position. The new buffer's position will be
   * 0, limit will be its capacity, and its mark is cleared. The new buffer's read-only property and
   * byte order are same as this buffer.
   *
   * <p>The new buffer shares its content with this buffer, which means either buffer's change of
   * content will be visible to the other. The two buffer's position, limit and mark are
   * independent.
   *
   * @return a sliced buffer that shares its content with this buffer.
   * @since Android 1.0
   */
  public abstract CharBuffer slice();

  /**
   * Returns a new char buffer representing a sub-sequence of this buffer's current remaining
   * content.
   *
   * <p>The new buffer's position will be {@code position() + start}, limit will be {@code
   * position() + end}, capacity will be the same as this buffer. The new buffer's read-only
   * property and byte order are the same as this buffer.
   *
   * <p>The new buffer shares its content with this buffer, which means either buffer's change of
   * content will be visible to the other. The two buffer's position, limit and mark are
   * independent.
   *
   * @param start the start index of the sub-sequence, referenced from the current buffer position.
   *     Must not be less than zero and not greater than the value obtained from a call to {@code
   *     remaining()}.
   * @param end the end index of the sub-sequence, referenced from the current buffer position. Must
   *     not be less than {@code start} and not be greater than the value obtained from a call to
   *     {@code remaining()}.
   * @return a new char buffer represents a sub-sequence of this buffer's current remaining content.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid.
   * @since Android 1.0
   */
  public abstract CharSequence subSequence(int start, int end);

  /**
   * Returns a string representing the current remaining chars of this buffer.
   *
   * @return a string representing the current remaining chars of this buffer.
   * @since Android 1.0
   */
  public String toString() {
    StringBuffer strbuf = new StringBuffer();
    for (int i = position; i < limit; i++) {
      strbuf.append(get(i));
    }
    return strbuf.toString();
  }

  /**
   * Writes the given char to the current position and increases the position by 1.
   *
   * @param c the char to write.
   * @return this buffer.
   * @exception BufferOverflowException if position is equal or greater than limit.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer append(char c) {
    return put(c);
  }

  /**
   * Writes all chars of the given character sequence {@code csq} to the current position of this
   * buffer, and increases the position by the length of the csq.
   *
   * <p>Calling this method has the same effect as {@code append(csq.toString())}. If the {@code
   * CharSequence} is {@code null} the string "null" will be written to the buffer.
   *
   * @param csq the {@code CharSequence} to write.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than the length of csq.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer append(CharSequence csq) {
    if (csq != null) {
      return put(csq.toString());
    }
    return put("null"); // $NON-NLS-1$
  }

  /**
   * Writes chars of the given {@code CharSequence} to the current position of this buffer, and
   * increases the position by the number of chars written.
   *
   * @param csq the {@code CharSequence} to write.
   * @param start the first char to write, must not be negative and not greater than {@code
   *     csq.length()}.
   * @param end the last char to write (excluding), must be less than {@code start} and not greater
   *     than {@code csq.length()}.
   * @return this buffer.
   * @exception BufferOverflowException if {@code remaining()} is less than {@code end - start}.
   * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid.
   * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer.
   * @since Android 1.0
   */
  public CharBuffer append(CharSequence csq, int start, int end) {
    if (csq == null) {
      csq = "null"; // $NON-NLS-1$
    }
    CharSequence cs = csq.subSequence(start, end);
    if (cs.length() > 0) {
      return put(cs.toString());
    }
    return this;
  }

  /**
   * Reads characters from this buffer and puts them into {@code target}. The number of chars that
   * are copied is either the number of remaining chars in this buffer or the number of remaining
   * chars in {@code target}, whichever is smaller.
   *
   * @param target the target char buffer.
   * @throws IllegalArgumentException if {@code target} is this buffer.
   * @throws IOException if an I/O error occurs.
   * @throws ReadOnlyBufferException if no changes may be made to the contents of {@code target}.
   * @return the number of chars copied or -1 if there are no chars left to be read from this
   *     buffer.
   * @since Android 1.0
   */
  public int read(CharBuffer target) throws IOException {
    if (target == this) {
      throw new IllegalArgumentException();
    }
    if (remaining() == 0) {
      return target.remaining() == 0 ? 0 : -1;
    }
    int result = Math.min(target.remaining(), remaining());
    char[] chars = new char[result];
    get(chars);
    target.put(chars);
    return result;
  }
}
